1. Field of the Invention
This invention relates to methods to determine the durability and wear-resistance of fabrics and soft armor.
2. Description of the Related Art
Soft body armor used by military and law enforcement organizations is subject to criteria not imposed on hard armor products. Particularly, the National Institute of Justice (NIJ), through their Technology Assessment Program (TAP), operates a body armor testing program to ensure that protective equipment worn by law enforcement personnel meets NIJ-established minimum performance requirements. Among the specific criteria are requirements for durability and wear-resistance. There are currently no accepted test methods specifically designed to gauge these properties for soft body armor. The incumbent methods are borrowed from other textile industries and tend to test and measure the effect of stresses on single layers of a composite. Results are then scaled to draw conclusions on the characteristics of an assembled multi-layer article. Such extrapolation can be inaccurate and can cause misconceptions about the performance of a multi-layer composite. Direct measurement of these durability and wear-resistance characteristics on the assembled multi-layer composite would lead to more accurate conclusions.
The lack of armor specific test protocols for durability and wear-resistance has led to the use and acceptance of inappropriate test methods that accelerate the effect of a mechanical influence on an article. These types of tests tend to fall into two categories. The first category are those tests that exaggerate the forces and conditions imposed on an article with the intention of forcing failure. The second category of tests uses appropriately scaled forces and conditions and cycles the article through a very large number of perturbations in a condensed period of time. Appropriately scaled forces will give a more realistic gauge of the expected performance of an article.
Based on observations of the condition and appearance of soft body armor that has been exposed to varying lengths of field service, generalizations can be made as to the nature of the forces and stresses that the articles have experienced. The subsequent impact of these perturbations on the ballistic performance of the article is measurable. Observations on field tested articles of soft body armor indicate that the materials are subject to a combination of flexing, tensile, compressive and abrasive forces. The methods of the present invention can duplicate those forces and stresses in a controlled, isolated, measurable, appropriate and intuitive manner to correlate ballistic performance with durability and wear characteristics. These tests and testing apparatuses are designed to achieve close approximation of the forces experienced in the end use of ballistic resistant composite articles.